ALSA: ua101: fix crash when unplugging

If the device is unplugged while running, it is possible for a PCM
device to be closed after the disconnect callback has returned.  This
means that kill_stream_urb() and disable_iso_interface() would try to
access already-invalid or freed USB data structures.

The function free_usb_related_resources() was intended to prevent this,
but forgot to clear the affected variables.

Reported-and-tested-by: Olivier Courtay <olivier@courtay.org>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: 2.6.33+ <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/misc/ua101.c b/sound/usb/misc/ua101.c
index 67bec76124421d12d7250675d6526a98bb886597..c0609c2103035b15df5e6d83694fae95d4723115 100644 (file)
--- a/sound/usb/misc/ua101.c
+++ b/sound/usb/misc/ua101.c
@@ -459,7 +459,8 @@ static void kill_stream_urbs(struct ua101_stream *stream)
        unsigned int i;
 
        for (i = 0; i < stream->queue_length; ++i)
-               usb_kill_urb(&stream->urbs[i]->urb);
+               if (stream->urbs[i])
+                       usb_kill_urb(&stream->urbs[i]->urb);
 }
 
 static int enable_iso_interface(struct ua101 *ua, unsigned int intf_index)
@@ -484,6 +485,9 @@ static void disable_iso_interface(struct ua101 *ua, unsigned int intf_index)
 {
        struct usb_host_interface *alts;
 
+       if (!ua->intf[intf_index])
+               return;
+
        alts = ua->intf[intf_index]->cur_altsetting;
        if (alts->desc.bAlternateSetting != 0) {
                int err = usb_set_interface(ua->dev,
@@ -1144,27 +1148,37 @@ static void free_stream_urbs(struct ua101_stream *stream)
 {
        unsigned int i;
 
-       for (i = 0; i < stream->queue_length; ++i)
+       for (i = 0; i < stream->queue_length; ++i) {
                kfree(stream->urbs[i]);
+               stream->urbs[i] = NULL;
+       }
 }
 
 static void free_usb_related_resources(struct ua101 *ua,
                                       struct usb_interface *interface)
 {
        unsigned int i;
+       struct usb_interface *intf;
 
+       mutex_lock(&ua->mutex);
        free_stream_urbs(&ua->capture);
        free_stream_urbs(&ua->playback);
+       mutex_unlock(&ua->mutex);
        free_stream_buffers(ua, &ua->capture);
        free_stream_buffers(ua, &ua->playback);
 
-       for (i = 0; i < ARRAY_SIZE(ua->intf); ++i)
-               if (ua->intf[i]) {
-                       usb_set_intfdata(ua->intf[i], NULL);
-                       if (ua->intf[i] != interface)
+       for (i = 0; i < ARRAY_SIZE(ua->intf); ++i) {
+               mutex_lock(&ua->mutex);
+               intf = ua->intf[i];
+               ua->intf[i] = NULL;
+               mutex_unlock(&ua->mutex);
+               if (intf) {
+                       usb_set_intfdata(intf, NULL);
+                       if (intf != interface)
                                usb_driver_release_interface(&ua101_driver,
-                                                            ua->intf[i]);
+                                                            intf);
                }
+       }
 }
 
 static void ua101_card_free(struct snd_card *card)